This invention relates generally to threaded fastener assemblies and, more particularly, to threaded fastener assemblies employed in applications where shear loads are present.
Threaded fasteners of this particular kind are frequently used to secure an outer panel to an inner panel, where the back side of the inner panel is inaccessible. Typically, such fasteners include a threaded nut, held loosely and prevented from turning by a cage attached to the inaccessible side of the inner panel. A mating bolt extends through appropriately sized and aligned apertures in the two panels and the cage, to threadedly engage the nut.
Before the bolt is tightened, the nut is free to float within the cage and thereby to move laterally into alignment with the bolt. Once the bolt is tightened, the nut moves into compressive engagement with the facing surface of the cage. At that time, the nut's freedom to move laterally within the cage is reduced, but not eliminated, by the friction between it and the facing surface of the cage. The nut's freedom to move laterally and seat anywhere within the cage, even when axially compressed by the bolt against the cage, limits the fastener assembly's capacity to carry shear loads imparted by or to the bolt. Consequently, these loads are borne largely by the aperture formed in the panel, which is in contact with the bolt. A prolonged exposure of this type can enlarge the aperture to a point where the fastener assembly becomes incapable of transferring shear loads and can require time consuming and costly replacement or rework of the inner panel.
In other cases, it is desirable to enlarge the aperture in the inner panel, to accommodate the float of the nut within the cage and thereby facilitate a convenient use of the fastener assembly when the panels are misaligned. This purposeful enlargement of the panel aperture can diminish the assembly's ability to transfer shear loads.
It should, therefore, be appreciated that there is a need for a threaded fastener assembly capable of effectively transferring shear loads. The present invention fulfills this need.